Examine the blood and prostate levels of carcinogens, selected by the Project Officer, when administered to laboratory animals, these levels should be compared with similar levels determined in other tissues with the body. Administer chronically those carcinogens having a high affinity for the prostate using direct prostatic urethra injection and other routes as necessary. Surgically esteriorize the canine prostate for the purposes of each of observation of organ changes during carcinogen administration. Perform gross pathological observations and histologically examine the various prostatic lobes by light microscopy of all animals that die or are sacrificed. Examine other organs for significant changes as required.